Hepatic ischemia and reperfusion (IR) injury contributes to the morbidity and mortality associated with liver transplantation. microRNAs (miRNAs) constitute a family of noncoding RNAs that regulate gene expression at the posttranslational level through the repression of specific target genes. Here, we hypothesized that miRNAs could be targeted to enhance hepatic ischemia tolerance. A miRNA screen in a murine model of hepatic IR injury pointed us toward the liver-specific miRNA miR122. Subsequent studies in mice with hepatocyte-specific deletion of miR122 (miR122^loxP/loxP Alb-Cre⁺ mice) during hepatic ischemia and reperfusion revealed exacerbated liver injury. Transcriptional studies implicated hypoxia-inducible factor–1α (HIF1α) in the induction of miR122 and identified the oxygen-sensing prolyl hydroxylase domain 1 (PHD1) as a miR122 target. Further studies indicated that HIF1α-dependent induction of miR122 participated in a feed-forward pathway for liver protection via the enhancement of hepatic HIF responses through PHD1 repression. Moreover, pharmacologic studies utilizing nanoparticle-mediated miR122 overexpression demonstrated attenuated liver injury. Finally, proof-of-principle studies in patients undergoing orthotopic liver transplantation showed elevated miR122 levels in conjunction with the repression of PHD1 in post-ischemic liver biopsies. Taken together, the present findings provide molecular insight into the functional role of miR122 in enhancing hepatic ischemia tolerance and suggest the potential utility of pharmacologic interventions targeting miR122 to dampen hepatic injury during liver transplantation.

Remote ischemic preconditioning (RIPC) is known to have a protective effect against hepatic ischemia-reperfusion (IR) injury in animal models. However, the underlying mechanism of action is not clearly understood. This study examined the effectiveness of RIPC in a mouse model of hepatic IR and aimed to clarify the mechanism and relationship of the ATP-sensitive potassium channel (K_ATP) and HMGB1-induced TLR4/MyD88/NF-κB signaling. C57BL/6 male mice were separated into six groups: (i) sham-operated control, (ii) IR, (iii) RIPC+IR, (iv) RIPC+IR+glyburide (K_ATP blocker), (v) RIPC+IR+diazoxide (K_ATP opener), and (vi) RIPC+IR+diazoxide+glyburide groups. Histological changes, including hepatic ischemia injury, were assessed. The levels of circulating liver enzymes and inflammatory cytokines were measured. Levels of apoptotic proteins, proinflammatory factors (TLR4, HMGB1, MyD88, and NF-κB), and IκBα were measured by Western blot and mRNA levels of proinflammatory cytokine factors were determined by RT-PCR. RIPC significantly decreased hepatic ischemic injury, inflammatory cytokine levels, and liver enzymes compared to the corresponding values observed in the IR mouse model. The K_ATP opener diazoxide + RIPC significantly reduced hepatic IR injury demonstrating an additive effect on protection against hepatic IR injury. The protective effect appeared to be related to the opening of K_ATP, which inhibited HMGB1-induced TRL4/MyD88/NF-kB signaling.

In the liver, reactive oxygen species (ROS) are constantly released during cellular metabolic processes, and excess ROS production can cause redox stress. The redox stress is both beneficial for and harmful to the survival of cells since it modulates the cellular redox control system. The redox control system is a series of cellular responses that are responsible for maintaining a balanced oxidation-reduction status. Many cellular processes including growth, proliferation, and senescence are sensitively regulated by the redox control system. Imbalance of redox induces redox stress and damages DNA, proteins, and lipids in cells, and further contributes to the pathogenesis of severe diseases and disorders like cancer. However, the cellular redox control system also utilizes redox stress-responsive pathways and increases antioxidant enzymes to aid cell survival. Therefore, a deeper understanding of the connection between the redox control system and liver disease is likely to pave the way for the future development of new therapeutic strategies. This review will examine the redox control systems in liver with responsive regulating molecules, current knowledge of the redox control system and liver disease, and suggest potential therapeutic targets for liver diseases.

Human liver-derived stem cells (hLD-SCs) have been proposed as a possible resource for stem cell therapy in patients with irreversible liver diseases. However, it is not known whether liver resident hLD-SCs can differentiate toward a hepatic fate better than mesenchymal stem cells (MSCs) obtained from other origins. In this study, we compared the differentiation ability and regeneration potency of hLD-SCs with those of human umbilical cord matrix-derived stem cells (hUC-MSCs) by inducing hepatic differentiation. Undifferentiated hLD-SCs expressed relatively high levels of endoderm-related markers (GATA4 and FOXA1). During directed hepatic differentiation supported by two small molecules (Fasudil and 5-azacytidine), hLD-SCs presented more advanced mitochondrial respiration compared to hUC-MSCs. Moreover, hLD-SCs featured higher numbers of hepatic progenitor cell markers on day 14 of differentiation (CPM and CD133) and matured into hepatocyte-like cells by day 7 through 21 with increased hepatocyte markers (ALB, HNF4A, and AFP). During in vivo cell transplantation, hLD-SCs migrated into the liver of ischemia-reperfusion injury-induced mice within 2 h and relieved liver injury. In the thioacetamide (TAA)-induced liver injury mouse model, transplanted hLD-SCs trafficked into the liver and spontaneously matured into hepatocyte-like cells within 14 days. These results collectively suggest that hLD-SCs hold greater hepatogenic potential, and hepatic differentiation-induced hLD-SCs may be a promising source of stem cells for liver regeneration.

Liver cancer exhibits the fourth most common cause of cancer‑associated mortality worldwide. Due to the rapid growth, solid tumors undergo severe hypoxia and produce high levels of extracellular adenosine to maintain homeostasis. A previous study indicated that the hypoxic condition in liver cancer increased hepatic adenosine, which is known to facilitate cancer survival and proliferation. Extracellular adenosine has been revealed to regulate pathological and physiological processes in cells and tissues. However, its pathophysiological role in liver cancer remains undetermined. Emerging evidence has indicated that the adenosine A2B receptor promotes the progression of liver cancer. Therefore, it was hypothesized that HIF‑1α is a transcriptional regulator of A2B in human liver cancer. The current study determined A2B expression of a number of liver cancer cell lines and performed functional studies of HIF‑1α as a master transcriptional regulator of hepatic A2B signaling during hypoxic conditions. The current study aimed to identify the promoter region of A2B, which has a hypoxia response element, by performing luciferase assays. The present study demonstrated that reduced HIF‑1α expression is associated with low expression of A2B, and HIF‑1α overexpression is associated with A2B induction. Furthermore, the siRNA‑mediated downregulation of A2B inhibited the growth and proliferation of HepG2, which is a liver cancer cell line. The relationship between HIF‑1α and A2B expression was also identified in human liver cancer specimens. In conclusion, the current study indicated that A2B is induced by the HIF‑1α transcriptional regulator during hypoxia, and it may be a potential pharmacologic and therapeutic target for the treatment of patients with liver cancer.

Hepatic intrasinusoidal (HI) natural killer (NK) cells from liver perfusate have unique features that are similar to those of liver-resident NK cells. Previously, we have reported that HI CD56^bright NK cells effectively degranulate against SNU398 hepatocellular carcinoma (HCC) cells. Thus, the aim of this study was to further investigate the phenotype and function of HI NK cells. We found that HI CD56^bright NK cells degranulated much less to Huh7 cells. HI CD56^bright NK cells expressed NKG2D, NKp46, TNF-related apoptosis-inducing ligand (TRAIL), and FAS ligand (FASL) at higher levels than CD56^dim cells. SNU398 cells expressed more NKG2D ligands and FAS and less PD-L1 than Huh7 cells. Blockade of NKG2D, TRAIL, and FASL significantly reduced the cytotoxicity of HI NK cells against SNU398 cells, but blockade of PD-L1 did not lead to any significant change. However, HI NK cells produced IFN-γ well in response to Huh7 cells. In conclusion, the cytotoxicity of HI CD56^bright NK cells was attributed to the expression of NKG2D, TRAIL, and FASL. The results suggest the possible use of HI NK cells for cancer immunotherapy and prescreening of HCC cells to help identify the most effective NK cell therapy recipients.